tylerwerrin

Hi guys,

I've been doing some diagnostic work on my car, and I've noticed that my LTerm Counts in DataMaster are coming in at 108. They go up from time to time, but normally they are hovering around 108 -- very rarely do they make it to the desired 128.

My STerm Counts are usually OK -- sometimes slightly low (125/126). What can I do about addressing this problem? I know the car is running rich because I can smell it -- It's been a nagging problem for a while.

New Opti, plugs, wires, coil, fuel pressure regulator & recently had the fuel system cleaned.

I have TunerCats, so I can change the tables -- but I don't know why the LTerm Counts would be so low.

Any help would be great!

Thanks,

Tyler W.

Dave89IROC

Any vacuum leaks? How old are the o2 sensors?

Sent from my PC36100 using Tapatalk 2

tylerwerrin

don't think i have any vacuum leaks -- i don't get any of the other symptoms (wandering idle, etc.) -- I replaced the intake gasket a few months ago, and checked the torque on each bolt recently.

O2 sensors are basically brand new -- maybe 500 total miles on them.

tylerwerrin

should i just program out the o2 sensors altogether? I could run off the MAF & MAP, right?

Kevin Blown 95 TA

you need your O2 sensors unless you want to run it in open loop all the time..

tylerwerrin

What about my MAF sensor? Does anyone have a chart on how a perfectly functioning MAF sensor reads while under load, idle etc? A mechanic i called today said it could be the temp sender, but it's basically new (a year old or so), and hasn't had more than a thousand miles on it.

my o2 sensors are basically new... but perhaps they were busted out of the box?

I'm just not sure what to try next... I checked around for exhaust leaks, and everything seems OK -- there are no "puff" or "ticking" sounds, and i felt around the down pipe, and i don't feel any exhaust escaping.

I'm not running any Cats -- could it be some weird backpressure thing?

tylerwerrin

i picked up a new MAF at lunch today and I'm gonna swap it in (good ol kragen and their great return policy...) -- I'll see what happens. If its not the MAF then it is the O2 sensors or some other question mark... does anyone have any ideas on what to try next? this rich problem is gonna keep ruining my plugs & o2 sensors...

Injuneer

Is the engine stock?

Has this always been a problem, or did it develop recently?

In which Cells do the BLM's get closer to 128? In which Cells are the 108? Are the left and right BLM's close to each other?

Have you checked for exhaust leaks before the O2 sensors?

What does DataMaster tell you the coolant temp sensor is reading? Is the system in closed loop? If the CLT sensor is indicating a temp high enough for the PCM to kick into closed loop, it's probably OK. What is the temp when fully warmed up?

As far as the MAF is concerned, you'll see anywhere from 6-10 GPS at idle, and upwards of 240-250 GPS at WOT/max RPM. The output from the MAF sensor is a variable frequency? Do you want the stock PCM table for Hz vs GPS? Is the MAF sensor facing in the correct direction? Has it been cleaned?

Since the fuel pressure regulator has been replaced and the fuel system cleaned, can we assume you have verified the fuel pressure?

If you post a link to the DataMaster log, I'll take a look at it.

tylerwerrin

Yes the engine is stock -- no modifications, and almost all new parts (o2s, coil, wires, plugs, opti, fuel pressure regulator & intake gaskets.)

The car always has run rich, and I've been trying to solve it for some time.

The car seems to use Cell 17 when it is running at 108 for the LTerm counts. The Sterm counts hover around 126/125. The Left and Right cells are basically the same -- within a single digit usually.


I got new downpipes installed (flange mounted, with a large circular gasket... the headers are "Rams Horn" type) and the problem persists. I don't hear any exhaust leaks, but I don't know of another way to check for them.

The Coolant sensor reads 84.5C in Closed Loop -- yes the system kicks into closed loop after a couple minutes.

The MAF has never been cleaned -- i purchased a used one off the forum. I noticed that it was descreened. I see 8.xx GPS at idle and when under load, the MAF reads up to around 40~.

I don't have a pressure meter, so no I haven't measured fuel pressure.

Where would you like me to post it? Its too large of a file to post to the forum (280k). Could I email it?

Thanks Injuneer!

Injuneer

First choice would be for you to upload it to an FTP site. Then anyone can download it.

tylerwerrin

I uploaded the file to my drop box. You can find it here:

http://dl.dropbox.com/u/24984984/apr...fter%20hub.uni

Let me know what you think!

Injuneer

The only important Cell that is at 108 is the idle cell (16). 17 is used in open loop (where it defaults to 128), and for decel in closed loop. That's when it's at 108. The other low load cells are nowhere near 108 (more like 120 min), and as you go toward higher load cells, the BLM's are actually above 128 (10 is as high as you managed to go in the data log).

I'd say it's pointing to a small vacuum leak. But the idle Map is exceptionally low, indicating a very healthy intake manifold vacuum. Have you checked for vacuum leaks on the ower end of the fuel injectors, where they poke into the manifold?

Try cleaning the MAF. Might be some dirt affecting the readings primarilly at very low air flows. Or try and find a screen.

tylerwerrin

Thanks so much for checking it out for me Fred. I'll take a look at the injectors -- do you mean the o-ring seals? I replaced those when i installed the fuel pressure regulator, so they are basically new. I'll look around for other possible places for air leaks... and try a new MAF, to see what happens.

tylerwerrin

injector seals appear fine -- i sprayed some starter fluid around the holes, and nothing changed the engine rpm. i went over to Autozone and picked up a new MAF to test with.

I brought the car over to my muffler guy who checked for any exhaust leaks. He said it all looked good.

I'm going to run another log today with the new MAF to see if that has changed anything.

bobdec

Tyler, Don't forget to reset the PCM to clear the LT BLM's after changing the MAS. If it dosent fix things can I ask you if the MAS, injectors and PCM all came from the same '94 donor car ? Also if you still have problems can you post up the .bin file (tune) you are currently using. As I said in the other post your PCM is doing a super job pulling 15% fuel correcting as shown by the ST BLM almost in range. If problem persists I'd like to see your tune settings for engine displacement, Injector constant, and MAF tables to compare them to stock.